In many processing environments, vapor (e.g., water vapor) is generated and utilized in connection with various processes. In the context of abating undesirable substances that result from fabrication processes (e.g., semiconductor fabrication processes), for example, there have been attempts to implement vapor delivery systems to convert undesirable byproducts to safer compounds for disposal in accordance with environmental guidelines and/or regulations.
As a specific example, water vapor has been utilized in connection with plasma processing devices to convert undesirable perfluorinated gases into relatively harmless components including carbon dioxide. Water vapor for such reactions may be provided by conventional water vapor delivery systems that function under relatively normal pressure conditions to provide water vapor at or above about 100° C. There are several drawbacks to using these conventional water vapor delivery systems. For example, these systems typically require substantial amount of energy, and hence, cost to vaporize water on a large scale.
Another approach to generating vapor includes equipping an evaporation chamber with hot plate evaporators to transfer the heat required to vaporize a liquid. These evaporators, however, are expensive to operate and are typically unable to deliver the volume of vapor needed for effective abatement of undesirable effluents.
An alternate water vapor delivery system uses a water evaporation chamber to heat a larger quantity of water to a temperature high enough to provide vapor on demand in combination with a vapor or gas mass flow controller (MFC), in a vapor feed line, to meter the amount of vapor that is allowed to flow out of the vaporization chamber to a plasma reactor. Although this type of system overcomes some of the drawbacks of the previously described system, it is still necessary to keep the entire system (including a relatively large amount of deionized (DI) water) at a continuously high temperature (e.g. between 90° C. and 140° C.), which drives up thermal costs and introduces safety concerns for workers interacting with such systems.
In yet another approach, low-temperature vapor is generated at sub-atmospheric pressures. Although this approach allows vapor to be generated at low temperatures, the liquid (e.g., water) is prone to freezing, which prevents the generation of vapor. One approach to solving this problem includes monitoring the temperature of the liquid and raising the temperature of the liquid when it approaches the freezing point of the fluid.
Problematically, measuring the temperature at the surface of the liquid, as the liquid is being vaporized, is difficult, and measuring the temperature of the liquid below the surface may not provide an accurate and/or timely measurement of the surface temperature—where the liquid is prone to freezing. Although the liquid may be actively stirred to help ensure the subsurface measurement is accurate, stirring the liquid requires energy and involves mechanical components that require maintenance and are prone to failure.
As a consequence, present devices are functional, but they are not sufficiently accurate or otherwise satisfactory. Accordingly, a system and method are needed to address the shortfalls of present technology and to provide other new and innovative features.